chore: Add Claude session temp files to gitignore

- Ignore .claude-mcp-*.json session config files
- Ignore .claude-prompt-*.md system prompt files
- These are ephemeral files created during chat sessions

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -105,3 +105,7 @@ _dat_run*.dat
 **/gnn_data/
 **/checkpoints/
 *.npz
+
+# Claude session temp files
+.claude-mcp-*.json
+.claude-prompt-*.md